The present invention relates to motor vehicle bearings and materials therefor and more particularly to a multilayer metallic bearing material which has a layer of aluminum or aluminum-base alloy, and to a process for making the bearing and bearing materials.
It is to be understood when the word aluminum is used in the present application it is intended to mean aluminum and aluminum-base alloys. Additionally, the word overlay as is known in the art is being used to denote that surface layer of a multilayer bearing material that actually comes in contact with a journal or other moving part.
It is known in the prior art to make a multilayer bearing with a backing layer of steel, an intermediate layer of aluminum and a top bearing surface or overlay. The adherence of the overlay on the aluminum surface has always been a problem. Conventionally, the overlay layer is electroplated onto the aluminum surface of the steel and aluminum composite in a multi-step plating process. This multi-step plating operation is expensive to perform and, due to its complexity, difficult to control. In many cases the bearing material may have to be passed through four or more separate plating baths and numerous auxiliary operations. Additionally, the bearing is typically electroplated in its final shape which may be that of a semicylindrical shell. This mode of operation means each bearing has to be individually handled on plating jigs or racks to yield a uniform, reliable plate.
It is also known in the prior art, as described in U.S. Pat. No. 4,071,643 to produce a multilayer bearing material with an aluminum intermediate layer by tinning or coating the aluminum surface and then casting the overlay on the coated aluminum surface. This method produces a bearing material which requires two distinct process operations; a coating step and an overlay-casting step. This multi-step process is expensive and can lead to reliability problems.
Accordingly, it is an object of the present invention to provide an improved multilayer bearing having a layer of aluminum and the process for making the bearing material.
It is another object of the present invention to provide a process for making a multilayer bearing material which is highly reliable and low in cost to manufacture.
It is yet another object of the present invention to provide a process for making a continuous uniform strip for bearings.
It is still another object of the present invention to provide a process for making bearing material which has good performance characteristics in both wear resistance and fatigue resistance.
It is yet still another object of the present invention to provide a method of applying an overlay layer on the aluminum layer of a multilayer bearing material in a single-step operation. Other objects and features will be in part apparent and in part pointed out hereinafter.
Accordingly, one aspect of the present invention concerns a multilayer bearing material which comprises bonding an outer overlay material to an aluminum layer of an aluminum-on-steel composite in a single operation.
Another aspect of the present invention concerns a method for making a bearing material comprising providing a composite material with a steel backing layer and an intermediate aluminum layer bonded to the steel and passing the composite material through a molten bath of an overlay material to securely bond the overlay material to the aluminum layer of the composite.
Still another aspect of the present invention concerns a method of making a bearing material comprising providing a composite material strip with a steel backing layer and an intermediate aluminum layer bonded to the steel, passing the composite strip through a molten bath of overlay material suitable for providing good adhesion to the aluminum layer, removing surface oxide from the aluminum layer thereby allowing uniform adherence of the molten material to the aluminum layer, and removing the composite strip from the bath and simultaneously controlling the uniform thickness of the overlay over the width of the strip.
Yet still another aspect of the present invention concerns a method of making a bearing material comprising providing a composite material strip with a steel backing layer and an intermediate aluminum layer bonded to the steel, passing the composite strip through a molten lead, tin, and zinc alloy bath of overlay material, removing surface oxide from the aluminum layer and removing the composite strip from the bath and simultaneously controlling uniform thickness of the overlay over the width of the strip.